An ink-jet recording method has been developed and widely used because it has various merits. For example, materials for the method are available at a low cost, and high speed recording can be accomplished. Further, the method makes relatively low noise, and easily utilizable for full-color recording.
As the ink-jet recording method, three types are known. One is a method in which drops of ink are pressured to be ejected by means of a piezoelectric element. In another method, bubbles are formed in ink by heating so that the bubbles would push out drops of the ink. The other is a method in which drops of ink are sucked and ejected with electrostatic force. As the ink for the method (i.e., jet printing ink), various kinds of ink such as aqueous ink, oily ink, and solid (melting) ink have been used.
Dyes used for the ink must satisfy various conditions. For example, they must be highly soluble in a solvent, and they must have excellent hues. It is also necessary for the dyes to have high resistance against light, heat, air, water and chemicals. Further, they must be well fixed onto an image-receiving sheet without blotting. They are furthermore required to have long shelf lives, to have no toxicity, to have high purity, and to be available at a low cost. However, there are few dyes fully satisfying those conditions, and in particular it is desired to develop dyes having excellent magenta or cyan hue and high resistance to light.
Various dyes or pigments have been proposed and practically employed for ink-jet recording, but there is no dye (or pigment) fully satisfying all the aforementioned conditions. Conventional dyes or pigments (such as those having C.I. Number) cannot satisfy the conditions of both having high resistance and giving hues necessary for ink-jet recording. Japanese Patent Provisional Publications No. 61-36362 and No. H2-212566 disclose jet printing inks. Those inks give satisfying hues and have good durability, but the dyes disclosed in the Publications have not enough solubility in water to prepare an aqueous ink. Further, even if the dyes are used in aqueous ink, the prepared ink has poor resistance against heat and moisture.